Resin blend of ethylene alpha olefin interpolymer and heterogeneous interpolymer for liquid packaging films

Abstract

This invention relates to bags and pouches made from films for packaging of flowable materials, in particular liquids that are made from blends of polyethylene and polypropylene useful to in addition to possessing good flex crack resistance, these films can withstand steam sterilization and/or aseptic packaging conditions as they have Hot Tack Initiation Temperatures in the range of from about 100° C. to about 140° C. and Hot Tack Strengths of not more than 5 N/inch in the temperature range from 100° C. to 150° C.

What is claimed is: 
     
       1. A bag or pouch for containing flowable material, made by a process comprising the steps of:
 (I) providing a monofilm, said monofilm comprising a flowable material packaging film comprising at least a resin blend of:
 (a) from about 33 wt % to about 80 wt % of at least one ethylene-C 4  to C 10 -α-olefin interpolymer having a melt-index of from 0.4 to 1.5 g/10 min (190° C., 2.15 kg), and a density of from 0.900 to 0.916 g/cm 3 ; and 
 (b) from about 67 wt % to about 20 wt % of at least one propylene-based heterogeneous interpolymer of propylene with ethylene, or of at least one propylene-based heterogeneous of propylene with ethylene and butene, said propylene-based heterogeneous interpolymer comprising:
 (i) from about 71 mol % to about 86 mol % propylene, and 
 (ii) from about 29 mol % to about 14 mol % ethylene or ethylene and butene, 
 wherein said propylene-based heterogeneous interpolymer has an overall weight average molecular weight (M W ) of at least about 400,000, a xylene soluble phase of not less than 30 wt %, with the xylene soluble phase having a M W  of at least about 275,000, and 
 wherein said propylene-based heterogeneous propylene-based interpolymer has a density of from 0.875 to 0.91 g/cm 3 ; 
 
 wherein said monofilm has a Hot Tack Initiation Temperature in the range of from about 100° C. to about 140° C. and a Hot Tack Strength of not more than about 5 N/inch in the temperature range of about 100° C. to about 150° C., when fabricated at a thickness of about 50 μm and tested using a JB Instrument Hot Tack Tester set at a 0.5 second dwell, 0.2 second delay time, 40 psi seal bar pressure, and 250 mm/second peel rate; and 
 wherein said monofilm has a flex crack resistance such that it develops 5 or less pinholes per 300 cm 2  in 10,000 cycles of Gelbo Flex testing as measured according to ASTM F392; 
 
 (II) forming said monofilm into a tubular member; 
 (III) heat-sealing longitudinal edges and then filling said pouch with flowable material; 
 (IV) heat-sealing a first transverse end of said tubular member to form a pouch; and 
 (V) sealing and cutting through a second transverse end of said tubular member to provide a filled pouch; said tubular member being filled continuously or intermittently; wherein said upper transverse seal is the bottom seal of the next pouch to be formed and filled; 
 and 
 wherein said monofilm has a thickness of from about 20 to about 150 μm. 
 
     
     
       2. The bag or pouch as recited in  claim 1 , wherein said monofilm is sterilized. 
     
     
       3. A bag or pouch for containing flowable material, made by a process comprising the steps of:
 (I) providing a multilayer film, said multilayer film comprising a flowable material packaging film comprising at least a resin blend of:
 (a) from about 33 wt % to about 80 wt % of at least one ethylene-C 4  to C 10 -α-olefin interpolymer having a melt-index of from 0.4 to 1.5 g/10 min (190° C., 2.15 kg), and a density of from 0.900 to 0.916 g/cm 3 ; and 
 (b) from about 67 wt % to about 20 wt % of at least one propylene-based heterogeneous interpolymer of propylene with ethylene, or of at least one propylene-based heterogeneous interpolymer of propylene with ethylene and butene, said propylene-based heterogeneous interpolymer comprising:
 (i) from about 71 mol % to about 86 mol % propylene, and 
 (ii) from about 29 mol % to about 14 mol % ethylene or ethylene and butene, 
 wherein said propylene-based heterogeneous interpolymer has an overall weight average molecular weight (M W ) of at least about 400,000, a xylene soluble phase of not less than 30 wt %, with the xylene soluble phase having a M W  of at least about 275,000, and 
 wherein said propylene-based heterogeneous propylene-based interpolymer has a density of from 0.875 to 0.91 g/cm 3 ; 
 
 wherein said multilayer film has a Hot Tack Initiation Temperature in the range of from about 100° C. to about 140° C. and a Hot Tack Strength of not more than about 5 N/inch in the temperature range of about 100° C. to about 150° C., when fabricated at a thickness of about 50 μm and tested using a JB Instrument Hot Tack Tester set at a 0.5 second dwell, 0.2 second delay time, 40 psi seal bar pressure, and 250 mm/second peel rate; and 
 wherein said multilayer film has a flex crack resistance such that it develops 5 or less pinholes per 300 cm 2  in 10,000 cycles of Gelbo Flex testing as measured according to ASTM F392; 
 
 (II) forming said multilayer film into a tubular member; 
 (III) heat-sealing longitudinal edges and then filling said pouch with flowable material; 
 (IV) heat-sealing a first transverse end of said tubular member to form a pouch; and 
 (V) sealing and cutting through a second transverse end of said tubular member to provide a filled pouch; said tubular member being filled continuously or intermittently; wherein said upper transverse seal is the bottom seal of the next pouch to be formed and filled; 
 and 
 wherein at least one layer of said multilayer film has a thickness of from about 20 to about 150 μm. 
 
     
     
       4. The bag or pouch as recited in  claim 3 , wherein said multilayer film is sterilized.